Before making a skin incision for spine surgery, it is necessary to locate the vertebral segment that contains the pathology and which is the target of the operation. Currently, this task is performed by needle localization.
In needle localization, the surgeon estimates the location of the skin incision based on palpation of anatomical landmarks, inserts a needle into the skin and advances it toward the spine. An X-ray is obtained. The surgeon then compares the location of the needle on the X-ray image to the known level of pathology based on pre-operative imaging studies (e.g. MRI or CT scan) and determines if his estimate was correct. If not, the needle is repositioned and the X-ray procedure is repeated until the correct spinal segment is located.
While not incident to surgery and not relevant to finding the incision site using X-rays, the use of laser beams to aid in detecting spinal abnormalities is known. For example, U.S. Pat. No. 4,832,049 discloses an apparatus for detecting an abnormality of the spinal column using at least one laser light beam obliquely applied to each of the left and right backs of a subject in parallel with an imaginary spinal line. The '049 patent permits detection of the imbalance of protuberances of the left and right backs based on the curvature of the spinal column. The prior art represented by the '049 patent is in general diagnostic evaluation for determining the existence of a spinal abnormality, but is generally not sufficiently specific as to the surgical incision point, that is for localizing the site in preparation for surgery.
The use of radio-opaque markers with X-rays is also known. For example U.S. Pat. No. 7,241,045 discloses radio-opaque markers attached to a frame in a stereoradiographic device having an X-ray source and a vertical X-ray receiver. The present invention uses at least one radio-opaque cable but in a device and configuration that is not disclosed in the prior art.